Does anyone have access to the Wheelsmith Rim Rod ERD measurement tool?

I need to reproduce this no longer manufactured tool.

Specifically, I need the length of the yellow portion of each rod, the diameter of the yellow portion of each rod, and the length and diameter of the alloy portion of the rod. Bonus points for the angle of the nipple seat at the join of the alloy portion and the yellow portion.

3 Answers
3

$59.91 seems a decent price when you're thinking about constructing your own from scratch.
–
EhrykApr 15 '12 at 9:41

That's not the question I asked. I'm aware of the ebay offerings, but my location makes ordering them online problematic. I know they will not be difficult to make, I just need the measurements. (I already own one set, but they are back in the States in my FIL's basement.) Also, for the record, I will never up vote and probably downvote any answer which has this tone. Really? Starting your answer with "Why bother?" How about because I want to?
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zenbike♦Apr 15 '12 at 10:30

I mistook the question then, because you mentioned "I need to reproduce this no longer manufactured tool." Obviously you are interested in the measurements in spite of them being readily available, so I wasn't being as helpful as I thought on my initial reading.
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EhrykApr 15 '12 at 18:29

I don't know if this asks the answer, but having myself either handled high-precision instruments before, and fiddled with inner rim diameter myself, before, I would consider these things:

Even if you HAD the instrument yourself, in your hands, It would be actually difficult to measure, annotate and manufacture the dimensions precisely. I think even if you take the original to a metal-machining shop, some precision would always be lost;

There would be no way to be sure anyone of us measure it right, even if we were most interested in this reverse engineering process (I am, for sure, but I don't have the tool unfortunately).

Most times, reverse engineering is a process where reproducing the WORKING PRINCIPLE of a tool is much more important than reproducing the EXACT DIMENSIONS of the tool.

So, what I would suggest you to do is:

Study and understand exactely what is the working principle of this tool. It seems to me it is to fit rods with nipple-shaped endings inside diammetrically opposed holes in a rim, and then measure the distance between the two other endings of the known-sized rods, so you can know some key distance, that I would define as the distance between the flat parts of the nipple's head. Having a spoke ending there would allow for maximum thread contact without the spoke thread prodruding towards the tube, also with a comfortable tolerance of 1 or 2mm shorter spokes being perfectly useable.

Considering this working principle, take the most similar things possible: actual spokes with glued nipples in the thread ends, and some precisely placed measuring zones in the elbow side:

The elbows themselves. You could tie them together, measure the distance, and add this distance to the already-known rod lengths;

Some smart-shaped-object, like a piece of a metal ruler, rigidly fixed (glued?) in place of the elbow;

The naked tips of the wires after removing the elbows.

If this is done thoroughly, I think it is perfectly possible to achieve, with no great expense and no great work, a level of precision more than anough to build a wheel within the relatively loose tolerance allowed by spoke/nipple thread lengths.

I know this is not the answer for your question, but I think these considerations might be of your interest.

This is a great answer. Unfortunately, my need in this case is more specific. I am aware of other methods of getting the spoke lengths I need, and I have thought about the points that you bring up here. What I need is the dimensions of the tool, as a beginning to revers engineering a spoke measurement formula that is existing, and based on the Wheelsmith tools. My intent is to recreate them, so that I can determine the fixed measurement system which is using them, so that I can accurately build a replacement which doesn't need them. I know there are options. This is a self education project.
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zenbike♦Apr 15 '12 at 19:52

I will keep studying these issues, too. When I have evolved more around that, I'll probably post a question about the possible ways of measure and calculate these things. Good luck!
–
heltonbikerApr 15 '12 at 20:17

By the way, the most problematic thing about the "theory" of rim diameter measurement is that the actual diameter DEPENDS on the shape/interaction of nipple heads and rim holes, which is FAR from standardized. Hopefully, I think, the tolerance might get to comfortable 2mm given the thread lengths, and any controlled measure, even not-high-precision, might achieve that.
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heltonbikerApr 15 '12 at 20:19